I'm in the middle of managing the development of a financial data warehouse.
The warehouse is being releases in 3 phases. The second phase, which is
being scoped now, requires the inclusion of some additional data sources.
My designers say that it takes about 2 months to first analyze and then
design the source to target mapping, changes to the DW, new ETL jobs, etc
before we start building the code. Since our DW is small currently about 22
tables in an Oracle database, I'm thinking that 40 man days is very
conservative and I'm thinking 20 man days per new source is probably more
like it.

Are there any opinions out there to support either view?

Paul